Every accountant I know swears by the powers of Excel. But not every accountant can harness that power as beautifully as Cary Walkin, an accountant from Canada. Walkin made a full RPG game inside Excel. As in you can use Excel to actually have fun.

The game, called Arena.Xlsm, can be downloaded here. It works with Excel 2007 and 2010 but hasn't been tested with Excel 2013 (it should work though). Unfortunately, like all things wonderful about Excel, Arena.Xlsm won't work on the Mac version of Excel. Gameplay includes:

Random enemies: Over 2000 possible enemies with different AI abilities.